1. Field
The invention relates to a dynamic bone anchor and a method of manufacturing a dynamic bone anchor. The dynamic bone anchor comprises an anchor member for anchoring to a bone or a vertebra, and a longitudinal core member provided in the anchor member, a portion of which is movable with respect to the anchor member. The core member is made, at least partially, of a material comprising a nickel-titanium (Ni—Ti) based shape memory alloy having superelastic properties. The method of manufacturing such a dynamic bone anchor makes use of the shape memory effect of the material of the core member. The dynamic bone anchor is particularly applicable in the field of dynamic bone fixation or dynamic stabilization of the spinal column.
2. Description of the Related Art
A dynamic bone anchor is known, for example, from US 2005/0154390 A1. The shaft of the bone anchor comprises an elastic or flexible section.
A further dynamic bone fixation element is known from US 2009/0157123 A1. The dynamic bone fixation element includes a bone engaging component and a load carrier engaging component. The bone engaging component includes a plurality of threads for engaging a patient's bone and a lumen. The load carrier engaging component includes a head portion for engaging a load carrier and a shaft portion that at least partially extends into the lumen. The distal end of the shaft portion is coupled to the lumen and at least a portion of an outer surface of the shaft portion is spaced away from at least a portion of an inner surface of the lumen via a gap so that the head portion can move with respect to the bone engaging component. The load carrier engaging component may be made from a high strength material, for example, a strong metal or metal alloy such as CoCrMo, CoCrMoC, CoCrNi or CoCrWNi. In a particularly preferred embodiment, the bone engaging component is made from titanium or a titanium alloy, while the load carrier engaging portion is made from cobalt chrome (CoCr).